All those packages updates improve the original system release by pushing it forward, like rolling continuously.

When CentOS produces a new minor version like 7.5.1804 they publish a new “minimal” ISO image.
The NethServer developers add a small RPM set on that image together with a kickstart file.
The resulting image is the NethServer ISO, with installer, server-manager and other stuff.

When NethServer 7.5.1804 is released, any existing 7.4.1708 installation can be upgraded seamlessly,
because both CentOS and NethServer ensure compatibility between minor releases.